This invention relates to data display and, more particularly, to a method for visually displaying intervisibility data relative to an observation point.
There are commercially available data bases of digitally stored terrain altitudes at grid points in terrestrial areas. Typically, such a data base comprises terrain altitudes in a square area of land mass of one degree latitude and one degree longitude, which is of the order of 100 km, and the grid points are spaced three arc seconds apart, which is of the order of magnitude of 100 meters.
One use of a terrain altitude data base is to determine intervisibility, i.e., whether a specified point on the surface of the earth is visible from an observation point, or if not, the height above the specified point that is visible from the observation point. There are presently computer algorithms for calculating intervisibility, i.e., line-of-sight between two points. These algorithms require complicated interpolation of the terrain altitude data base, essentially random access to the data base stored in computer memory, and a large number of calculations to develop intervisibility data relative to an observation point. The larger the terrestrial area under study the greater is the processing time required to make the intervisibility data available for visual display.
There are a number of uses for a visual display of intervisibility data, including artillery placement, short-range air defense, ground surveillance and threat avoidance. These uses become more appealing and varied as the time and computer complexity required to produce the data decreases.